The invention relates particularly to a wrench for use with drilling apparatus used for drilling holes into the ground with a drill rod comprising a drilling segment, extension segments and a distance piece, the distance piece, in use, being engaged by the drilling apparatus, thereby to connect the drill rod to the drilling apparatus. The above segments of a drill rod are hereinafter referred to merely as drill rod segments.
As part of a drilling operation, extension segments of a drill rod must be located in line with or removed from the drill rod, which requires adjacent segments of the drill rod, connected via complementary threads in a spigot and socket fashion, to be loosened with respect to one another. Insofar as the thread configuration of drill rod segments of a drill rod provide for segments to be tightened together during drilling, a wrench, referred to herein as a drill rod wrench, that is operatively mounted on the support structure of a drilling apparatus, is provided for loosening adjacent segments, many different configuration drill rod wrenches being already well known. Each of these drill rod wrenches provides essentially for a drill rod segment to be gripped between opposing jaws and for the wrench to be displaced around the drill rod gripped, for loosening thereof.
A particular drill rod wrench that forms the subject matter of the Applicant's U.S. Pat. No. 6,817,271 comprises a gripping arm, that defines a mouth formation locatable around a drill rod segment and that has gripping formations located thereon, and a lever arm, that defines a wedge face and that is pivotally connected to the gripping arm, particularly in a configuration in which initial pivotal displacement of the lever arm with respect to the gripping arm provides for the wedge face defined thereby to act on the drill rod segment to be gripped for urging the drill rod segment into gripping engagement with oppositely located gripping formations of the gripping arm. Continued displacement of the lever arm then provides for loosening of the drill rod segment relative to an adjacent segment, the force applied by the wedge face on the drill rod segment for urging into gripping engagement with the gripping formations, due to its relative displacement with respect to the drill rod segment, increasing until loosening of the drill rod segment occurs. The displacement of the lever arm is induced by a piston/cylinder mechanism acting between the lever arm and the support structure of the drilling apparatus, the exact configuration of the wrench being clearly apparent from the disclosure of the Applicant's abovementioned patent,
It has become apparent that the drill rod wrench forming the subject matter of the Applicant's abovementioned patent is very effective in relation to the required loosening of adjacent drill rod segments, but insofar as the general configuration of different drilling apparatus requires a wrench to operate within different space parameters, the wrench as originally envisaged and as covered in the above patent cannot be employed in association with all drilling apparatus. As such, it is an object of this invention to provide an alternative configuration drill rod wrench which can operate in a relatively more restricted space, while still utilising the gripping arrangement, including a gripping arm and a lever arm as above envisaged, for gripping a drill rod segment.